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practical meaning to a land manager. In the first place, the index is blind to <br />desirability of the species contributing to it. An increase in the occurrence <br />of the number of undesirable species for example, could result in an increase <br />in the estimated diversity index. Conversely, an increase in the occurrence of <br />the number of desirable species could result in a lower estimated diversity <br />index. The biases applied to the data to .calculate the index are based on <br />highly theoretical ideas of what plant diversity really is. These ideas are <br />not agreed upon by researchers in the field nor is it understood exactly what <br />they mean in terms of land management or utility. <br />Finally, and most importantly, one must be aware that to compare a portion <br />of an undisturbed, natural and relatively stable community (permanent reference <br />site) against what will be a changing and different community (at least for <br />most of an operator's liability period) by a standard which is subjective in <br />design and intent, is extremely statistically and legally questionable. As it <br />now exists, the diversity index obtained is simply a number that is largely <br />meaningless since it cannot be compared to any known standard for management <br />purposes. In the past, land managers have relied on a few simple measurements <br />of vegetative expression to allow evaluations of diversity as it related to the <br />planned land use. Species composition for example, not only provides a list of <br />species present (richness) but also indicates the relative occurrence of each <br />species (dominance). Species frequency is another parameter that has long been <br />used to indicate the distribution of species. These parameters are well estab- <br />lished in the literature and are well accepted by land managers and research- <br />ers. While they may not incorporate all of the components of diversity, it is <br />important to keep in mind that such components are poorly defined, poorly <br />understood and even more poorly agreed on. While they provide fertile ground <br />for research, they are not well enough understood or accepted to apply as cri- <br />teria to evaluate the success of revegetation for legal purposes. <br />-9- <br />5,.; 21*z <br />